"In the West, sunny skies are accelerating crop development and fieldwork, although monsoon showers have expanded across the Four Corners Region," USDA says.

On the Plains, excessive heat is exacerbating drought in southern growing areas, where today's highs will once again approach or exceed 100°F, USDA reports. "Drier, warmer weather on the northern Plains is allowing spring wheat harvesting, although colder air is approaching from the northwest," USDA says.

In the South, USDA says varying degrees of drought persist from Texas into the Southeast, where increasingly hot conditions are rapidly offsetting the benefits of last week's rain. "However, showers are falling in the northern Delta and southern Florida, providing some drought relief," USDA reports.

USDA's outlook calls for unsettled weather to overspread much of the eastern half of the nation. "The greatest likelihood of heavy rain will be across central portions of the Plains and Mississippi Valley, as monsoon moisture from the Southwest interacts with a stalled frontal boundary," USDA says. "Showers will be somewhat lighter on the southern Coastal Plain, while locally heavy downpours are possible in southern Florida and the Northeast," USDA says. It continues, on the northern Plains, warm, sunny conditions will gave way to notably cooler weather, although precipitation -- if any -- will be light. "In contrast, dry, excessively hot weather will persist over the southern Plains, with daytime highs averaging more than 10°F above normal," USDA says. Out west, monsoon showers in the Four Corners will contrast with seasonably dry weather from the central and northern Rockies to the Pacific Coast, USDA explains.